Metallic lens directive antenna system



July 31, 1951 i w. E. KOCK METALLIC LENS DIRECTIVE ANTENNA SYSTEM 4 Sheets-She et 1 Fild April 8, 194a E-PL'ANE PATTERN or Hon/v qr FIG.

TRANSLATION DE VICE DEGREES INVENTOR W E. KOCK ATTORNEY I July 31, 1951 w. E.,KOCK

METALLIC LENS DIRECTIVE ANTENNA SYSTEM 4 Sheets-Sheet 2 Filed April 8, 1946 TRANSLA TION DE VICE //v v5/v TOR W E KOCK AT TORNEV July 31, .1951 w. E. KOCZK' METALLIC LENS DIRECTIVE ANTENNA SYSTEM Filed April 8, 1946 4' Sheets-Sheet s m w 2 a m V llm F. M z. EQBMQ M mw 1 m I|+ET m Dr nk 0 .H IHFMNO F [N m a 5 m w m Mm; W llm i W .A 0 lrm 9 n w 7 5 m m m O c mw mqmmvuwa m I. v% W m MM m n 0 fl l= II Hm 5 -m am w m 4 w E m 0 WM; m I. 3 JflP 0 A T TOR/Vi: V

July 31, 1951 I w. E. KOCK 2,562,277

METALLIC LENS DIRECTIVE ANTENNA SYSTEM Filed April 8, 1946 4 Sheets-Sheet 4 TRANSLA 7/0 05 VICE INVE N TOR n4 1 mm ATTORNEY Patented July 31, 1951 METALLIC LENS DIRECTIVE ANTENNA SYSTEM Winston E. Kock, Middletown, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application April 8, 1946, Serial No. 660,338

9 Claims. (Cl. 250-33153) This-invention relates to directive antenna systemsand-particularly to radio lenses used in such systems.

As disclosed, respectively, in Patent 2,283,935 I (Figs. 16 and 17) to A. P. King and in my copending application Serial No. 642,723, a flat cellular lens having a uniform thickness. and comprising a plurality of guides or cells,and a stepped multiple-zone plane-concave lens hav ing a non-uniform thickness and comprising one or more dielectric channels, have been proposed for focusing radio waves." While the uniform thickness feature of the flat lens may be advantageous in certain systems, the focusing action of this lens is considerably less than that of the plano-concave lens, since the fiat lens does not comprise a plurality of zones, whereas the 0011- cave lens comprises several zones. it now-appears desirable to utilize, for certain purposes, a lens having a uniform thickness and a-focusing action fairly-comparable to that obtained in the above-mentioned stepped multiplezone concave lens.

- It is one object of this invention, in a flat lens, to-obtain a greater focusing action than heretofore secured. 7

It is another object of this invention, in a linetype feed such as a sectoral horn, to focus the waves in the plane of the long dimension of the feed, in a moresatisfactory manner than heretofore accomplished. I

It is still another object of this invention to obtain a" simple, easily constructed radio lens having a uniform depth or thickness.

-.It is a further object ofthis'invention, in an antenna system comprising a sectoral horn, to

focus in all planes and especially in the E and a large piano-concave cylindrical lens and, when so utilized, focusing in both the E and H planes, that is, oniniplanar focusing, is secured.

In accordance with another embodiment, the

H-plane or so-called .a: dimension of a single Accordingly,

. 2 dielectric channel of uniform thickness is tapered, that is, the phase velocity characteristic, and hence the refractive index are tapered, for the purpose of securing focusing action. In accordance with another embodiment, an omniplanar lens having a point focus and a uniformthickness comprises a plurality of dielectric channels. :Each channel has a tapered refrac-- tive index and the refractive indices of cone-- the channels are tapered j sponding portions of or graded.

The invention will be more'fully understood from a perusal of the following specification taken in conjunction with the drawing on which like reference characters denote elements of similar function and on which:

Figs. 1, 2 and 3 are perspective, front and side .7

views, respectively, of one embodiment of the invention comprising a dielectric channel having a tapered refractive index, and Fig. 4 is a' measured directive pattern for this embodiment;

Figs. 5 and 6 are perspective and front views, respectively, of another embodiment of the ini vention comprising a plurality of channels hav- 1 each channel having a tapered index;

. Figs. 10, 11 and 12 are perspective, front and partial top views, respectively, of a sectoral'horn equipped with a stepped. fiat lens of the inven-;; tion, and Figs. 13, 14 and 15 are directive pat-- terns for the horn ofFigs; 10, 11 and 12; i Fig. 16 is a perspective view of a directive antenna system constructed in accordance with the invention and comprisinga main plano-concave 1 lens and the sectoral horn of Figs. 10, 11 and l2.v Referring to Figs. -1, 2 and 3-, reference numeral 1 denotes a sectoral horn having a mouth aperture 2 and a throat aperture 3, and numeral d denotes a guide connecting the throat aperture 3 to a translation device 5 such as a transmitter or receiver. The horn l is flared in the E-plane, which contains the electric polarization of the propagated wave and represented by the arrows; 5, but not in the H-plane 'l. The long and short. dimensions of the mouth aperture 2 are denotedhy the reference characters Z and m, respectively;

{IWli'llfil 8 denotes. a dielectric channel or lens mounted in the mouth aperture 2 of the horn l and having an electromagnetic axis 29. The lens 8 comprises the wedge-shaped wall members 9 and the air dielectric medium included therebetween. The depth d of the channel 8 is uniform and both the front face I!) and the back face ll of the lens 8- are plane, so that the lens is of the plano-plano or flattype. As shown on the drawing, the Width or a dimension of channel 8 is tapered from a maximum value m at the midpoint to equal minimum values a at the top. and bottom extremities. Hence, and as explained in my copending application mentioned above, the phase velocity characteristic and the refractive index of the channel are tapered. The phase velocity of the channel 8, consideredin its entirety, is greater than that of free space; and the phase velocity increases from a minimum at the mid-point or widest portion of the channel to a maximum at each end or narrow channel portion. In one embodiment actually constructed and tested the dimensions I, m, n and d, mentioned above, have values in wavelengths, M, as measured in the air of 6.76M, 0.77M, 0.56M and 1.54m, respectively, the design wavelength to being: 3.4 centimeters.

In transmission, waves supplied by device to guide 4 and horn I are propagated through the lens 8 and thence radiated. More particu larly, as shown in Fig. 3, waves originating at the throat aperture 3 have a circular wave front, represented by the lines l2, in the E-plane. Since the phase velocity is. greater at the top and bottom than at the center, the top and bottom portions of the wave front are advanced more rapidly in phase than the central portion so that the lens: 8 converts the circular front to a linear Wave front f3. In the H-plane, the front of the emergent wave is also substantially linear, so that the outgoing wave front is flat or plane.

Considered differently, the lens 8 functions to produce in the E-planea very sharp beam, as shown in Fig. 4. In Fig. 4, numeral I4 denotes the major lobe and numerals l5 denote the minor lobes of the E-plane pattern I6. The major lobe is relatively sharp since its width taken at the half power point IT is only 8.6 degrees. Also the minor lobes are below fifteen decibels and therefore negligible. Without the lens 8, the beam established by the sectoral horn would be a so-called fan-beam. With the lens 8 in position, however, a point type beam is established. In reception the converse operation obtains, and the lens focuses the incoming rays on the throat aperture 3.

Referring to Figs. 5 and 6, reference numeral 18 denotes a fiat quasi-rhombic channel lens comprising a plurality of dielectric channels 8 and having a line focus I9 and an electromagnetic axis 29. Each channel comprises two adjacent plate-members 20 and the air dielectric therebetween. The plates 20 are'held in position by the wooden members 2|. While the channels 8 are each electrically the same as the channel 8 of Fig. l, the outer channels are bent at the center and the end or narrow channel portions are positioned close together, so as to form a compact structure. Numeral 22 denotes a vertically polarized line feed or array aligned with the focal line l9 and comprising the vertical dipoles 23. The dipoles are connected by the transposed conductors 24, 25 and the coaxial line 26 to a translation device 5. Numeral 2! denotes a plane reflector for the array 22.

In transmission, energy is supplied by device 5 over line 26 and conductors 24, 25 to the dipoles 23. The dipoles are energized in phase and establish a wave front which is circular in the E or vertical plane. In this plane the lens l8 functions to convert the circular wave front [2 to a linear front [3, whereby a high degree of directivity is secured. In; reception the incoming rays are focused by the lens [8. on the linear array 22 coincident with the focal line I9.

Referring to Figs. 7 and 8, reference numeral 28 denotes a three-zone flat lens having an axis 29 and a focal line 30. The lens 28 comprises a plurality of dielectric channels denoted by numerals. 31-60,. inclusive. The channels have a uniform depth d and different H-plane or a dimensions and each channel comprises a pair of metallic plates, 9 and the air dielectric included therebetween. The section of the lens 28 at. the right of axis 29 is divided into three half zones R1, R2, and R3 and, similarly, the section at the left is. divided into three half zones L1, L2 and L3. In more detail, the right central channels 3 l38 and the left centralchannels 4653' constitute the first or central zone RiLl; the right channels 3942' and the left: channels 54-51 constitute the second zone RzLz, and the channels 43-45 and 5860 constitute. the third zone RsLs. It will be noted that in each zone, the channels positioned at the left and right of axis. 29 and. spaced equally from axis29 have equal a dimensions; that is, channels 3l'--45 cor-- respond, respectively, to channels NS-60. The zones are full wavelength zones. Thus, the dis,- tances between the focus 30 and the junction points 5 l ofzones R1111 and RzLz. are each a wavelength N), as measured in air, greater than. the focal length I or distance between the focus: 3.0 and the iunction 62 on axis 29 of the two half zones R1 and L1. The distances between the junction. points 63 of zones R2L2 and RsLa. and the. focus 30 are each two wavelengths, 2A0, greater than f and the distances between the extremities 64 of zone RsLa are each 3m greater than J.

In each half zone, the a dimensions, and therefore the phase velocities and refractive indices for the several channels are selected so that. the differently phased waves emitted at the focus 30 and passing through the channels emerge from the. channels in like phase or, stated differently, so.

that a circular wave front originating at the focus 30 is converted to a plane wave front. Considering, for example, the channels 3l38 in the halfzone R1 the refractive index n of each channel is less than unity and, proceeding from the innermost channel 3| to the extreme channel 38 of the half-zone, the refractive indices for the channels. decrease. The actual values of the indices are determined by the so-called cut-and-try method and the corresponding a dimensions are determined from the following equations which are given in my copending application. Serial No. 642,723.

Hence, the number of channels in each half zone and the widthsof the channels are dependent upon the indices selected; and each half zone may include a plurality of channels differing from the plurality shown on the drawn. In one practical embodiment, designed for a wavelength of M equal to 3.3 centimeters, the depth d of the lens is 1.54 x; and the 11 dimensions of the fifteen right channels til-45, and the fifteen left channels 466|l, were, respectively, 1.23, 1.08, 0.884, 0.75, 0.655, 0.616, 0.576, 0.557, 0.964, 0.692, 0.608, 0.554, 0.964, 0.662, and 0.569,as measured in w velengths in the air. a

The primary antenna for energizing the lens 28 or receiving energy therefrom comprises a linear array 22 of vertical dipoles 23 each aligned with the focal line 30 of lens. 28. The dipoles 23 are positioned in front of a plane reflector 21 and are connected by the branch coaxial lines 65, and the main line 66 to a translation device 5.

In operation, Figs. '7 and 8, assuming device is a transmitter, the dipoles are supplied with radio waves over lines 56 and 65 and a wave having a linear front I3 in the E-plane 6 and a circular front |2 in the H-plane that is, a cylindrical wave, is emittedtoward the lens 28. In the H-plane, the lens 28 transforms the circular front l2 to a linear front l3 and, in the E-plane, the wave front is not changed, so that the emergent wave'has a plane wave front. Considered differently, in each of zones R1111, R2L2 and R3L3, the wavelets entering the innermost channel as, for example, channel 3|, arrive advanced in phase relativeto the wavelets arriving at the remaining channels as, for example, channel 32. The phase velocity of channel 32 is greater than that of channel 3| and-such that the two wave- Elets emerge in phase agreement. Hence, for any of the three zones, the wavelets emerging from the several channels of the zone are in phase. zones are in phase agreement since the phase angles of the wavelets outgoing from zone R1L1 differ by 360 and 720 degrees, respectively, from the wavelets outgoing from zones RzLz and RaLs. Since the lens has a plurality of zones the focusing action is relatively great and considerably.

greater than that obtainable in a single zone flat lens. In reception the converse operation obtains. More particularly, the linear wave front l3 in the H-plane 1, of the incoming waves is converted by the lens 28 into a circular'wave front |2 converging on the array 22 aligned with the focal line 30, that is, in the I-I-plane 1 the incoming rays are focused on the linear array 22. -In the E-plane 6, the incoming linear, wave front I3 is not changed by the lens 28.

I In the above description of the fiat lens of Figs.

7 and 8, it has been assumed that the dielectric;

medium in the several channels is air having a dielectric constant of unity. With the dielectric constant uniform throughout the lens, the a dimensions are proportioned to secure the focusingnotes a lens having an axis 69 and a focal point Ill and comprising a plurality of dielectric chan-' The-waveletsemerging from the three nels 10, II, 12, I3, 14, I5 and 16. Numeral l'l de notes a point-type horn positioned at the focalpoint' 10 and connected by the glide T8 to the translating device 5. The a dimension of each channel is tapered, asin the system of Figs. 1, 5 and 6, and the indices of the several channels are graded as in the system of Figs. 7 and 8. In each channel the maximum refractive index is less than unity and the index at the center of the channel is greater than that at each extremity.

Also, proceeding horizontally from the vertical axial plane 19, the maximum or dimensions, and

therefore the maximum refractive indices of the channels decrease, and the values of the minimum phase velocities for the channels increase. Simi-- larly, proceeding horizontally from the vertical axial plane 19, the minimum a dimensions decrease and the maximum phase velocities increase; and for intermediate points in the channels above or below, and spaced at equal distances from the horizontal axial plane 80, the a dimers-- sions decrease and the phase velocities increase;

As in the lens of Fig. 1, a taper for each channel is selected, by the cut-and-try method, so that the desired focusing in the E-plane 6 is obtained and, as in the system of Figs. '7 and 8, the refrac tive indices of the several channels are selected so that the desired focusing in the H-plane 1 is secured.

The operation of the system of Fig. 9 is believed to be obvious in view of the discussion given above in connection with Figs. 1, '7 and 8. Briefly, the

horn i1 emits a spherical wave front which, by reason of the focusing action of lens 68 in both the H and E-planes, is converted to a plane wave front. In reception, the incoming rays are fo-- cused in both planes upon the horn 11.

Referring to Figs. 10, 11 and 12, reference numeral 8| denotes a sectoral horn which is con-- nected by guide 18 to the device 5. The horn is flared in the H-plane I, but not in the E-plane 81, 88, 89, 90 and 9| denote the channels in half zones R4, R5 and R5; and numerals 929S designate the channels in the half zones L4, L5 and Le, In one embodiment of Figs. 10, 11 and 12, actually constructed and tested for a value of )\0=3.3

centimeters, the channels 3|45 and 48-50 in the three central zones R1111, RzLz and RaLs have the same a dimensions as those given above for a practical embodiment of Figs. 7 and 8. Also,

in the actual embodiment of Figs. 10, 11 and 12, d hasa value of 1.54M and the a dimensions of channels 849| and 9299 are, respectively,

0.955, 0.630, 0.554, 0.805, 0.600, 1.00, 0.615 and.

05502.5 measured in wavelengths M. The sectoral horn actually tested has an axial length G of,

the major lobe and numeral I03 designates the minor lobes. As shown in Fig. 13, the beam in the I-I-plane is very sharp, the width of the major lobe I02 at the half power point I04 being only 2.0 degrees. The measured gain of the horn of Fig. 10 over a standard reference antenna is 29.6 decibels. In the E-plane, the beam or major lobe of the horn 8| is somewhat wider so that a fan beam, rather than a point beam, is produced. The minor lobes I03 are below 20 decibels and are therefore negligible, as is desired.

Numerals I05 and I08, Figs. 14 and 15, designate the measured H-plane patterns taken at the side or off frequencies corresponding respectively, to 3.4 and 3.11 centimeters. Numerals I01 and I08 denote the major lobes, and numerals I09 and H denote the minor lobes of H-plane patterns I and I06, respectively; and numerals III and I I2 designate the half power points of major lobes I01 and I08, respectively. The half power widths III and H2 are, respectively, 2.08 and 2.5 degrees, and the minor lobes I09 and H0 are below 18 decibels. Hence, the three I-I-plane patterns I02, I01 and I08 are substantially the same and the lens 83 has a wide band characteristic.

As shown in Fig. 16 the sectoral horn 8|, equipped with a lens 83, may be used with advantage as a line feed for a passive antenna member such as a lens or a reflector having a line focus. In Fig. 16, numeral II3 designates a stepped plane-concave, cylindrically symmetrical, metallie, lens of the type disclosed in my copending application Serial No. 642,723. The lens II3 has a line focus H4 and an electromagnetic axis or axial plane I15, and comprises a plurality of dielectric channels H6. The long or I-I-plane dimension of the mouth aperture 82 of horn BI, and therefore the longitudinal or H-plane dimension of the fiat lens 83 is aligned with the focal line H4; and the axis II5 of lens II3 coincides with the axis 29 of lens 83. In order to secure optimum illumination of the main lens H3, the mouth aperture 82, and hence one face of the lens 83, is equipped with the horn flares I I! and associated end pieces II8. Numeral H9 denotes the throat aperture of horn 8I.

In operation, waves supplied by device 5 are focused, in the H-plane l, by the stepped flat cellular lens 83, as explained in connection with Fig. 10, and in this plane a very sharp beam is established. In the E-plane 8, the main lens I I 3 functions to focus the rays. Consequently, omniplanar focusing is secured. More specifically, considering transmission in the I-I-plane l, the lens 83 converts the circular wave front I? emanating from the horn throat aperture M9 to a linear wave front I3 at the horn mouth aperture 82. In the E-plane 8, the lens H3 converts a circular wave front I2 originating at the mouth aperture 82 to a linear wave front l3, whereby a flat front I3, I3 is established. In reception the converse operation obtains. The incoming rays are focused in the E-plane by lens I I3 on the fiat lens 83 and, in the H-plane, the rays are focused on the throat aperture II9 of .horn 8I by the flat lens 83. The throat aperture II-0, which is coincident with focal line 30, constitutes a primary antenna. Considered from another standpoint, the lenses 83 and H3 are each uniplanar, that is, each lens focuses in one plane only and, since the focal lines 30 and I I4 are perpendicular, the focusing planes are perpendicular.

Although the invention has been explained in connection with certain embodiments it. is to be understood that it is not to be limited to theembodiments described inasmuch as other apparatus may be employed in practicing the invention.

What is claimed is:

1. A sectoral horn having a pair of flared sides and a pair of parallel sides, and a metallic lens in the mouth of said horn, said lens comprisinga plurality of conductive plates positioned per- ;pendicularly with respect to the said pair of parallel sides of said horn, said plates subdivid ing the mouth aperture of said horn into wave passages varying in width across the mouthv of. the born by amounts related to the wavelength to focus waves transmitted through said horn and lens in a plane parallel to said parallel sides.

2. A fiat cellular metallic lens for focusing waves of a given wavelength, said lens having an axis and a focus, said, lens comprising a plu rality of adjoining zones positioned along a lineperpendicular to said axis and each comprising a plurality of metallic cells having different refractive indices each smaller than unity, said cells being positioned at different distances from said axis, the distances from the junctions of said zones to said focus differing from each other by a multiple, including the integer one, of' said wavelength.

3. A fiat cellular lens for focusing waves having a given wavelength and a given electric polarization, said lens having an axis and a focus and comprising a plurality of adjoining zones positioned along a line perpendicular to said. polarization, each zone comprising a plurality of metallic cells having different widths measured along said line and being positioned at difierentdistances along said line from said axis, the refractive indices of said cells being inversely related to the distances of the cells from said axis and the distances from, said focus to adjacent junctions of said zones differing a wavelength.

4. A fiat metallic lens for focusing waves having a given electric polarization, said lens having a uniform thickness and a focus and comprising at least two cells having equal refractive indices, each cell comprising conductive walls extending parallel to said polarization, one cell being a wavelength or a multiple thereof farther away from said focus than the other cell.

5. In combination, a sectoral horn having a pair of parallel sides and a pair of angularly related sides and a flat lens positioned in the mouth of said horn for focusing waves having a given electric polarization, said lens comprising a plurality of cells having different refractive indices, each cell comprising a pair of fiat conductive walls positioned parallel to said polarization.

6. In combination, a sectoral horn having a pair of parallel sides and a pair of angularly related sides, and a multiple-zone flat cellular lens in the mouth of said horn, said lens comprising conductive plates extending perpendicular to said parallel horn sides, providing wave passages proportioned in width with respect to one another in each zone to give an overall focusing effect.

7. In combination, a main lens having a line. focus, a sectoral horn having the long dimension of its mouth aperture aligned with said line focus and a multiple-zone flat lens in said aperture.

8. In combination, a main plano-concave lens having a line focus, a sectoral horn aligned with said focus, and an auxiliary lens positioned between said horn and said main lens.

9. A multi-zone lens, having a focus, for converting a wave front curved in one planeto a planar wave front or vice versa. comprising a linear array of parallel short sections of wave guides arranged side by side in a central zone and in one or more zones on'either side of said central zone the phase velocities of the guides within each zone increasing from guide to guide outwardly in either direction from the center of the lens, the junctions between adjacent zones being at respective distances from the focus differing by a wave length or integral multiple thereof.

WINSTON E. KOCK.

REFERENCES CITED The following references are of record in the file of this patent:

10 UNITED STATES PATENTS Number Name Date 1,332,410 Potts Mar. 2, 1920 1,496,652 Cooper June 3, 1924 1,958,996 Hansen et al May 15, 1934 2,035,827 Newell Mar. 31, 1936 2,283,935 King May 26, 1942 2,309,626 Conrad Feb. 2, 1943 2,376,428 Hansell May 22, 1945 2,405,242 Southworth Aug. 6, 1946 2,415,352 Iams Feb. 4, 1947 2,415,807 Barrow et al Feb. 18, 1947 OTHER REFERENCES On a Method of Decreasing the Reflection from Nonmetallic Substances, by John Strong, in the Journal of Optical Society of America, pp. 73 and 74, of January 1936, vol. 26. 

